serum vs plasma - hormone ELISA
Posted 04 January 2012 - 06:40 AM
Quick question - I have a set of plasma samples which we have access to to look at thyroid hormones using ELISA.
The kit specifies that serum should be used, not plasma.
I am not quite sure how / why plasma would interfere with the assay - any idea?
Is there a reasonable protocol out there to prepare plasma derived serum? I haven't come accross any and given that bloods were collected on anti-coagulant, this may not be feasible...
Hope someone can advise.
Posted 04 January 2012 - 05:58 PM
Posted 05 January 2012 - 03:55 AM
Kits already purchased previously by tech, and plasmas are not from in-house study.
Posted 06 January 2012 - 06:16 PM
Posted 11 January 2012 - 07:35 AM
you could prepare serial dilutions of the kit high calibrator in a normal plasma and with the kit 0 calibrator. If the curves are on top of one another then you are all set to go and analyze your samples. If the curves are different then you do have a matrix issue and will have to compensate for the difference.
Posted 18 January 2012 - 03:51 AM
I heard back from the company, who confirmed that they did not recommend plasma only because they did not validate the kit with that matrix, not due to actual interferences.
I have done pretty much what you suggested PAO - it looks good enough to go.
Otherwise - a quick thought - would the cryoprecipitation from thawing frozen plasma in the fridge pretty much remove any fibrinogen in the sample (thereby "correcting" the matrix effect once the precipitate is spun down and supernatant used)?
Posted 18 January 2012 - 12:34 PM
FYI......the small molecule kits are competative the TSH and TBG are probably sandwich type assays.